In electric power systems, especially high-voltage transformer substations, high-voltage switches and transformers connected by overhead lines are often used. This design requires a large amount of space, and there is the possibility of an accidental short circuit occurring between an overhead line and the ground, for example a short circuit caused by lightning. In this process, a high-voltage switch will be unable to protect a transformer, so that the transformer suffers damage. Moreover, once installed, high-voltage switches (e.g. ceramic column circuit breakers) and transformers occupy a large area of ground. With land resources becoming ever scarcer and more expensive, and requirements on the reliability of electric power systems becoming ever more exacting, this design needs to be improved.